Genetic and phenotypic diversity in 2000 years old maize (Zea mays L.) samples from the Tarapacá region, Atacama Desert, Chile

PLoS One. 2019 Jan 30;14(1):e0210369. doi: 10.1371/journal.pone.0210369. eCollection 2019.

Abstract

The evolution of maize (Zea mays L.) is highly controversial given the discrepancies related to the phenotypic and genetic changes suffered by the species, the incidence of human groups and the times in which these changes occurred. Also, morphological and genetic traits of crops are difficult to evaluate in the absence of fossils macro-botanical remains. In contrast in the Tarapacá region (18-21° S), Atacama Desert of Chile, prehispanic settlements (ca. 2500-400 yr BP) displayed extensive maize agriculture. The presence of archaeological macro-botanical remains of maize provided a unique opportunity to study the evolution of this crop, covering a temporal sequence of at least 2000 years. Thus, in this study, we ask how the morphological and genetic diversity of maize has varied since its introduction during prehispanic times in the Tarapacá region. To answer this, we measured and compared morphological traits of size and shape between archaeological cobs and kernels and 95 ears from landraces. To established genetic diversity eight microsatellite markers (SSR) were analyzed in archaeological and modern kernels. Genetic diversity was estimated by allelic frequency rates, the average number of alleles per locus, observed heterozygosity (Ho) and expected heterozygosity (He). Differences between populations and genetic structure were estimated by fixation index FST and STRUCTURE analysis. Our results indicate significant phenotypic differences and genetic distance between archaeological maize and landraces. This result is suggestive of an introduction of new varieties or drastic selective changes in modern times in Tarapacá. Additionally, archaeological maize shows a low genetic diversity and a progressive increase in the size of ears and kernels. These results suggest a human selection during prehispanic times and establish that prehispanic farmers played an important role in maize development. They also provide new clues for understanding the evolutionary history of maize in hyperarid conditions.

Publication types

  • Historical Article

MeSH terms

  • Alleles
  • Chile
  • Crop Production / history
  • Desert Climate
  • Evolution, Molecular
  • Genetic Variation
  • History, Ancient
  • Humans
  • Microsatellite Repeats
  • Phenotype
  • Selection, Genetic
  • Zea mays / anatomy & histology
  • Zea mays / classification
  • Zea mays / genetics*

Grants and funding

This research was funded by AVE, National Master Degree Scholarships, CONICYT, http://www.conicyt.cl/; LFH, FONDECYT 1150690 CONICYT, http://www.conicyt.cl/; MFP, FONDECYT 1171369 CONICYT, http://www.conicyt.cl/; MUR, FONDECYT 7060165 CONICYT, http://www.conicyt.cl/; MUR, FONDECYT 1130279 CONICYT, http://www.conicyt.cl/; MUR, FONDECYT 1181829 CONICYT, http://www.conicyt.cl/, and Facultad de Ciencias Sociales, Universidad de Chile.